The central aim of this study is to identify the molecular events associated with expression and control of a set of functionally related eucaryotic genes. During the past grant period we have constructed a powerful system with which to pursue this goal. It is the allantoin degradative system in Saccharomyces. Studied in greatest detail have been the last two enzymatic steps of the pathway which are probably catalyzed by a single multifunctional protein with a molecular weight of 202K daltons. A fine structure map of the locus responsible for production of the multifunctional protein is consistent with the above interpretation. With this work as a foundation, we feel that the following areas are most appropriate at the present time: (1) completion of physico-chemical studies to characterize the urea carboxylase-allophanate hydrolase multifunctional protein and production of specific antibody against it, (2) production of specific hybridization probes against the dal and dur genes, (3) elucidation of the events associated with production of functional urea amidolyase (the urea-carboxylase:allophanate hydrolase multifunctional protein), (4) explanation of the role played by the allantoin degradative enzymes in cellular homeostasis and (5) isolation and sequencing of the control sequences for a set of related eucaryotic genes.